1. Field of the Invention
The present invention relates to a substrate processing apparatus including a processing cup that includes a guard and a cup, and a processing cup cleaning method that cleans the processing cup.
Examples of substrates to be processed include semiconductor wafers, substrates for liquid crystal displays, substrates for plasma displays, substrates for FEDs (field emission displays), substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photomasks, ceramic substrates, substrates for solar cells, etc.
2. Description of Related Art
In a manufacturing process for a semiconductor device or a liquid crystal display device, etc., a substrate processing apparatus is used to process substrates, such as semiconductor wafers, glass substrates for liquid crystal display devices, etc. US2009320885 A1 discloses a single substrate processing type substrate processing apparatus that processes substrates one by one.
This substrate processing apparatus includes a spin chuck, rotating a substrate around a vertical rotational axis, passing through a central portion of the substrate, while holding it horizontally, a processing liquid nozzle, discharging a processing liquid toward an upper surface of the substrate held by the spin chuck, a cylindrical processing cup, surrounding the spin chuck, and an exhaust pipe, exhausting a gas in the processing cup.
The processing cup includes a plurality of guards, catching the processing liquid expelled outward from the spin chuck, and a plurality of cups, respectively catching the processing liquid guided downward by the plurality of guards. Each guard includes a cylindrical portion, surrounding the spin chuck, and a ceiling portion, extending obliquely upward toward the rotational axis from an upper end portion of the cylindrical portion. Each cup includes an annular bottom wall portion, surrounding the spin chuck, an inner wall portion, extending upward from an inner peripheral portion of the bottom wall portion, and an outer wall portion, extending upward from an outer peripheral portion of the bottom wall portion. The bottom wall portion, the inner wall portion, and the outer wall portion define an annular liquid receiving groove that is open upward. A lower end portion of the guard is positioned above the liquid receiving groove.
The processing liquid discharged from the processing liquid nozzle lands on an upper surface of the rotating substrate and thereafter flows outward along the upper surface of the substrate. The processing liquid that reaches an outer peripheral portion of the substrate scatters from the substrate to its periphery and is caught by the guards. The processing liquid caught by the guards flows downward along inner peripheral surfaces of the cylindrical portions of the guards and flow down into the liquid receiving grooves of the cups. The processing liquid in the cups is drained from the bottom wall portions of the cup. Also, a gas in the processing cup is exhausted to the exhaust pipe upon passing upward through gaps between the cylindrical portions of the guards and the outer wall portions of the cups.
The processing liquid, such as a chemical liquid, etc., remains on inner surfaces of the guards. The guards are thus cleaned at an appropriate timing. The cleaning of the guards is performed, for example, by making the processing liquid nozzle discharge pure water toward the spin chuck that is rotating in a state where a substrate is not held by the spin chuck. The pure water discharged from the processing liquid nozzle is supplied to the guards via the spin chuck and flow downward along the inner peripheral surfaces of the cylindrical portions of the guards. The pure water is thereby supplied directly to the inner peripheral surfaces of the cylindrical portions and the inner peripheral surfaces of the cylindrical portions are cleaned.
However, the pure water that flows downward along the inner peripheral surfaces of the cylindrical portions of the guards falls from lower ends of the cylindrical portions and it is thus unlikely for the pure water to directly contact lower surfaces and outer peripheral surfaces of the cylindrical portions. Although a chemical liquid flowing downward along the inner peripheral surfaces of the cylindrical portions is also unlikely to directly contact these portions (portions indicated by thick alternate long and short dashes lines in FIG. 13), a mist or liquid droplets of the chemical liquid may contact these portions. Especially with the substrate processing apparatus of US2009320885 A1, exhaust passes upward through the gaps between the cylindrical portions of the guards and the outer wall portions of the cups (see arrows shown in FIG. 13) and therefore the chemical liquid is likely to attach to outer peripheral surfaces of lower end portions of the cylindrical portions. There are thus cases where minute amounts of the chemical liquid remain on the lower surfaces and the outer peripheral surfaces of the cylindrical portions. When such a chemical liquid dries, crystals of the chemical liquid remain on the corresponding portions.